Vacuum is a medium for providing actuating force in some vehicles. For example, vacuum may be used to assist a driver to apply vehicle brakes. Vacuum may be sourced to actuators via an engine intake manifold, vacuum pump, or an ejector. Engine intake manifold vacuum may be a suitable vacuum source for naturally aspirated engines; however, there may be insufficient engine intake manifold vacuum for operating vacuum actuators when the engine is turbocharged. Therefore, vacuum may be provided for turbocharged engines via an ejector or a vacuum pump.
An ejector provides vacuum by way of providing a low pressure region in a flow path of a motive fluid. In some examples, the motive fluid may contain fuel vapors, untreated engine emissions, and/or engine crankcase vapors. If the ejector develops a leak, it may be possible for gases to enter the atmosphere. For example, an ejector leak may be manifested in a converging section, a diverging section, or a vacuum or suction section. Since pressure within the converging, diverging, and suction sections may vary significantly, it may require three or more sensors (e.g., a sensor in each section) to determine which, if any, ejector section is leaking. Consequently, it may be expensive and challenging to determine whether or not an ejector is leaking so that the engine control system can detect degradation and alert the driver and potentially take mitigating action. Further, it may be expensive or difficult to meet requirements of regulating agencies for determining if tubes that connect to an ejector have been disconnected.
The inventors herein have recognized the above-mentioned disadvantages and have developed a system for providing vacuum for a vehicle, comprising: an engine including an air intake passage; and a vacuum generating device including a motive fluid inlet section, a diverging discharge section positioned within the air intake passage, and a suction inlet.
By placing a diverging section of an ejector or a venturi within an engine air intake passage, it may be possible to avoid making measurements of the ejector diverging section to detect leaks in the diverging section since any leaks in the diverging section will be released into the closed boundary of the engine. Consequently, hydrocarbons or untreated exhaust gases entrained in the motive fluid, which provides vacuum via the ejector, are directed to engine cylinders where they may be combusted and then treated in the engine exhaust system. Additionally, a particular benefit of arranging an ejector within an engine air intake is that a disconnect or leak in the diverging section outlet may be unnecessary to detect because it is within the engine air intake. A connection at the diverging section is expensive to detect due to a requirement of additional pressure sensors within the diverging section.
The present description may provide several advantages. Specifically, the approach may reduce the need to monitor all sections of an ejector to diagnose the ejector for leaks. Further, the approach may reduce a number of sensors required to monitor an ejector for leaks. Further still, ejector leaks may be determined without adding any additional sensors to the vehicle system.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.